Consumers have been treating amino acid based substrate for years. Such treatments have included the waterproofing or coloring of textiles, the sunscreening of skin, the coloring, conditioning, and styling of hair, the dentifirce treatment of teeth, and more. It is well known that if such treatment can be done by some kind of safe covalent attachment to the substrate, that the treatment will be much more long lasting. Therefore, several reactive chemistries have been developed to provide covalent attachment to amino acid based substrates such as hair. Historically, these technologies, based on covalent attachment of cosmetic actives, have primarily relied upon electrophilic (electron accepting) and nucleophilic (electron donating) reactive groups or “hooks”. More recently, a Protected Thiols “hook” technology for the covalent attachment of cosmetic actives to amino acid substrates has been proposed.
It is highly desirable to formulate consumer products as aqueous solutions or aqueous emulsions for a number of consumer preferred attributes, e.g., ease of rinsing, aesthetic feel, less coating of bathroom tiles, environmental concerns, etc. However, attaining such aqueous compositions is problematic in the delivery of technologies for the covalent attachment of cosmetic actives to amino acid based substrates. The reactive groups or “hook” moieties which are reactive towards amino acid residues in hair protein are also reactive towards electron rich ingredients that are employed in the formulation of consumer products to deliver these actives, including water and even atmospheric oxygen. This leads to pre-mature decomposition of the hooks of covalent reactive compounds, referred to herein as reactive agents, over the shelf life of the product which severely or completely mitigates reactive efficacy with a substrate upon usage by the consumer.
The primary advantage of the present invention is the discovery of a delivery system approach that will enable the formulation and delivery of reactive agents to amino acid based substrates from an aqueous composition that is chemically shelf stable. This is accomplished via a delivery system wherein the reactive agent is solubilized within a suitable water immiscible solvent and then the solvent is emulsified within the aqueous phase into structured bi-layer phases, or bi-layers, which confers improved chemical shelf stability to the reactive agent. While not being bound to theory, it is believed that the water immiscible solvent comprising the reactive agent serves as a diffusion barrier that minimizes contact between the chemically unstable reactive agent and the aqueous phase. The structured bi-layers surrounding the water immiscible solvent are a further barrier between the reactive agent and the aqueous phase. The bi-layers also serve to keep the reactive agent dispersed within the aqueous continuous phase over the shelf life of the composition to enable the delivery of the reactive agent to the hair in a consumer preferable medium, i.e., an aqueous emulsion cream, and without additional consumer inconvenience.
Furthermore, on occasions wherein the reactive agent is charged, e.g., cationic, or anionic, the bi-layers can formed of surfactants with the same net charge of the reactive agent which acts as an even further barrier between the reactive agent and the aqueous phase via coulombic repulsive forces that repel the reactive agent from aggregating at the water/solvent interface.